Creo's FM network - Staccato

FM network printing has always been the most perfect way of screen image screening for all printers. It not only solves many problems such as hitting nets, moire, and moiré in multi-color printing, but also greatly enhances the details and levels of images. Almost all manufacturers of prepress printing equipment have their own FM screening technologies, such as Diamond Networks in Heidelberg, Crystal Networks in Agfa and so on. Of course, they also printed a lot of printed samples of the FM network, everything looks perfect. But...Ten years have passed, all this seems to have only stayed in the laboratory, and almost no one really applied this screening technology to the actual job at the time of printing.

why?

Because the CTF's workflow is lengthy, strict process control at each step is sometimes too difficult. The emergence of CTP solved the problem of the process to some extent. But even if it is directly imaged on the PS plate, the instability of dot expansion of small dots is still a serious problem. The solution to this problem is: "Square Laser Point Technology". Creo has conducted long-term and in-depth research on FM networks. From a technical point of view, we believe that square laser spot and secondary FM screening technologies are necessary factors to achieve a truly practical FM network. Both are indispensable.

● Square laser spot technology

The Creo square laser spot, which has won several awards for the new technology in the world, is not simply a square shape of the laser spot. The traditional CTP laser is a laser tube that emits a light spot for actual exposure, so the imaging point inevitably inherits the Gaussian energy curve of a single laser tube. Creo's square laser spot is cut through Creo's patented “light valve”. The energy curve is almost straight, and it can form a very steep spot on the plate. Don't worry about the impact of changes in the back-end processing conditions on the dot size. Compare the data in the left picture:

Imagine that if the size of the edge of the dot is only 1 μm, the unpredictable variation of 200 lpi of the traditional screened dots is less than 3%, but the uncontrollable change of the 10 μm-sized FM dots reaches 30%. If a print has 30% of outlets that cannot be adjusted, it means that the finished products we printed are completely unrepeatable, let alone quality control.

With “light valve”, Creo is one of the companies that can accurately control the laser edge to ±0.2μm (even if the back-end processing conditions are changed by 10%). We can control the expansion rate of the 10μm-size FM network. Within 4%.

● Secondary frequency modulation screening technology

Why is FM frequency screening twice?

A frequency-modulation screening method uses a random algorithm to fully disperse the dots in the original unit area. Therefore, there is a high probability of duplication in the midtones (50% of the flat screen). When multiple midtones are superimposed on each other, water-like waves appear. That is what we call low harmonics. In response to this phenomenon, we will first completely restructure the FM network and then break it again to obtain the required secondary FM network.

The expansion of the usual FM network screening network is relatively large. This is because the expansion of outlets only occurs at the edge of the outlets, and many small outlets after breaking up the original large-scale ATM outlets have a much larger total perimeter than their original outlets. Secondary FM screening adds links between neighboring small sites when they are reorganized, which greatly reduces the overall perimeter of the network, making it easy to control network expansion.

● The specific implementation of FM network printing.

1. It is the first step to get customer satisfaction with printing density and network expansion.

Printing consumables used by printing companies in mainland China are relatively complex and have poor process control for printing. Let us first look at the expansion of network expansion in an ideal environment (see Figure 1).

The actual situation (see Figure 2) is that the control of the film is relatively simple and the density and linearity can be easily controlled using a transmission densitometer. The printing version is confusing. Usually, 2% of outlets can still be used as a standard. Due to the lack of reliable inspection equipment, in fact, the loss of outlets is too large (usually around 10%), which ultimately leads to loss of control during printing.

Therefore, the use of AM outlets to print controlled prints with a constant outlet expansion rate is an effective means to enable customers to specify their goals. In general, Chinese customers do not want the printing dot expansion curve to look like European standards, but rather prefer brighter and lighter works. Therefore, Japan's printing characteristics curve is sometimes better, and of course it also needs to be adjusted according to customers' different inks and papers.

2. Measure the expansion rate of the printing outlets of the FM outlets.

The network expansion curve of Staccato's quadratic FM network is far behind that of the conventional AM network (see Figure 3). Since the network expansion can only occur at the edge of the network, the maximum network expansion of the AM network always occurs at 50% (the longest point of the network at that time). Looking again at Staccato, you will find that the total perimeter of the edge of the 75% dot is longer than 50%, so its dot expansion curve is also very special. This network expansion curve is also very special. This network expansion curve brings great advantages to actual printing, because the dot expansion usually becomes larger with the increase of the ink density, and the biggest change of the amplitude modulation network occurs in the middle tone, so the human eye can easily see the difference. (People are most sensitive to midtones). However, for Staccato, as the density of the ink increases, the dark tone first changes and the midtone change does not change significantly, so that the FM dot printing can easily ensure the consistency of the printing tone.

3. By adjusting the linear curve of Staccato, use FM network to simulate the outlet expansion rate approved by customers.

We have an actual measured curve and a target curve. All we need to do is use Staccato to simulate the output of the AM network (see Figure 4). All of this is much easier than you think.

At present, there are already two actual users in China using Staccato secondary FM outlets for printing. We hope that we can push China's printing quality to a new peak through extensive practical use of FM network printing!